Connecting fibers between ATFL's inferior fascicle and CFL transmit tension between both ligaments

The lateral ligament complex of the ankle has been extensively studied. Recently an anatomical study described a connection between anterior talofibular ligament inferior fascicle (ATFLif) and calcaneofibular ligament (CFL). The applicability and the mechanical role of these connections have not yet been studied and need to be clarified. The purpose of this study is to evaluate the connection between ATFLif and CFL through a dynamic measurement analysis.

An anatomical study was performed in 13 fresh-frozen below-the-knee ankle specimens. Each specimen was dissected in a protocolized manner until the lateral ligaments were exposed. A complete injury to both ATFL's fascicles was created in the proximal third of the ligament. A displacement transducer specifically design was inserted in the CFL and in the lateral part of the calcaneus to test its lengthening. A traction of 1 kg weight (9.8 N) was applied to ATFLif while the transducer measured the lengthening that this force created in the CFL.

A total of 13 ankle specimens were carefully dissected. One specimen with signals of a prior traumatic injury of the ATFLif was excluded. A total of 12 specimens were included, 7 females and 5 males with an average age of 74 years (52-88 years). The right ankle was dissected in 6 specimens. ATFL was identified as a two-fascicled ligament in all cases. The fibers connecting the ATFLif and CFL were observed in all specimens. The displacement transducer showed lengthening in the CFL in all measurements with a median of 0.59 mm (SD ± 0.34).

Connecting fibers between ATFLif and CFL are robust enough to transmit tension from one structure to the other. In the case of associated proximal lesions of the ATFLif and CFL, ligaments repair with a single suture may be considered. This can be applied in surgical procedures in patients with lateral ankle instability.